Economic efficiency drives the semiconductor industry, making space, speed, and cost of ownership important factors in capital equipment design. Space is important because facilities are hyper-expensive, often costing several billion dollars to construct. Owners of such facilities increasingly desire to tightly arrange machines in order to maximize return on investment. Thus, trends in capital equipment design are toward vertically stackable systems and machines with minimal floor footprint.
Speed is important because it determines output quantity. To increase manufacturing speed, fabrication and test systems are automated and modular. In a typical test system, robotic handling machines cycle articles to and from a modular test head, which contains measurement equipment. Depending on the measurements, the test head may be in “head over,” “head under,” or “vertical plane” position relative to the handler. The test head as a whole can be mounted and dismounted from the rest of the system using a manipulator, enabling rapid swapping of test heads or interface elements to perform different measurements, or for test head calibration, or for maintenance.
Cost of ownership is also important. For test head manipulators, cost generally scales with degrees of freedom and weight-bearing capacity. Thus, there is a cost-flexibility tension in manipulator design, which results in known test head manipulators being classified as “dedicated” or “general purpose.” Dedicated manipulators are typically fixed to another element of a test system and have customized design weight limits, size limits, and ranges of movement. Customization, however, adversely affects off-design applicability as test head weight, size, positioning or stacking requirements change. As a result, a dedicated manipulator may need time-consuming or expensive modification or replacement.
General-purpose manipulators, in comparison, are typically freestanding and have up to six degrees of freedom of movement. Design trade-offs necessary to achieve broad purposes, however, may render such manipulators as inappropriate for many applications as an off-design customized device; or may render the manipulator overly expensive.
In striking a design balance, many known general-purpose and dedicated manipulators employ hinges to support the weight of a test head while allowing rotation about the hinge's axis. Such hinged structures can bear thousands of pounds of test head weight and provide adequate freedom of movement, but disadvantageously require considerable headroom and floor space to accommodate the arc of the test head's swing. Moreover, should vertical translation be desired, other structures are needed in addition to the hinge, which increases cost.
What the semiconductor industry needs for increased space efficiency, instead, are compact, portable manipulators for translating and rotating a heavy test head into “head over,” “head under,” or “vertical plane” orientations, such functionality achieved with reduced floor space and headroom requirements and cost, and without customization.